Researchers in Britain have been tickling 22 apes and seeing how they laugh. To me, that’s an inherently fine idea. To those who insist on niceties like scientific purpose, it’s a new take on the study of evolution.
The project, co-ordinated by the University of Portsmouth, involved taking 800 audio samples from tickling apes of the four main species (orangutans, gorillas, chimpanzees and bonobos) plus three human volunteers.
The results not only show that laughter is not exclusive to humans, but that there’s a clear pattern to the way it has evolved over time across apes and humans. This evolution has happened very slowly across the last 10 to 16 million years, though the more rapid evolution of the past five million years means human laughter is very distinctive.
In comparing the species, the laughter of humans was closest to chimpanzees and bonobos, and furthest to orangutans. That fits in with most theories of how humans evolved from apes.
The study also threw up a totally unexpected result: gorillas and bonobos can laugh while exhaling for as much as four times longer than a normal breath. That trait, previously thought to be exclusive to humans, is a key part in the way human speech evolved.
Dr Marina Davila Ross, who headed the study, has previously found that orangutans at play will mirror one another’s expressions, which she says is one of the key factors behind laughter.
And now, to directly quote the university’s press release, in a line you’d never expect from an academic institution: Click to watch video of a juvenile orangutan being tickled.